Tuning the LUMO Energy of an Organic Interphase to Stabilize Lithium Metal Batteries

Interfacial stability is considered as a priority in high-energy lithium metal batteries (LMBs), stemming from the extremely low electrochemical potential of Li metal and its intrinsic high reactivity. The naturally grown solid-electrolyte interphase (SEI) containing organic compositions (e.g., R1OCOOR2, ROLi) and inorganic compositions (e.g., Li2CO3, Li3N) is thermodynamically unstable against Li metal. Herein, we created a highly stable organic interphase (HSOI) with a well-tuned LUMO energy to improve the antireduction ability of SEI components and enhance the long-term cyclability of LMBs. Employing trifluoromethyl functional groups (-CF3) in the molecule structure of a SEI can significantly tune the orbital energies and the HOMO-LUMO gap due to the strong electron-withdrawing property of -CF3 functional groups. With the protection of HSOI, cells can cycle more than 1300 h, which is 5-fold improvement in cell lifetime, demonstrating the vital role of the HSOI layer on the stability of LMBs.